1. Field of the Invention
The invention relates to heavy duty liquid detergents whose cellulose ether component is stabilized against lump formation and separation.
2. The Prior Art
Cellulose ether polymers have long been used in heavy duty liquid detergents to provide the properties of thickening, soil release and anti-redeposition. Thickening of aqueous formulations is desirable for both practical and aesthetic reasons. Liquids with a water-like viscosity are perceived by consumers as less effective than more viscous liquids. Thicker compositions tend to remain on soiled areas to which they are applied for pre-wash treatment. Longer residence time at soil sites improves directed cleaning ability.
Soil release refers to the protective coating of cellulose ether deposited onto the fabric in a previous wash. Removal of stains is facilitated in subsequent washes, the previously deposited soil release film forming a protective coating over the fabric.
Anti-redeposition properties refer to the cellulose ether ability to suspend soil in the wash liquor preventing reprecipitation of soil onto fabric. Accordingly, cellulose ethers are highly desirable components for liquid detergent formulations.
Unfortunately, heavy duty liquid detergents are fickle beasts. Shelf stability is not one of their noteworthy attributes. Liquid detergent formulations contain a cast of characters having mutually antagonistic properties. Organic surfactants must be reconciled with inorganic salts and water. Not least are the cellulose ethers which remain a difficult component to compatibilize within the liquid system.
Freeze-thaw and low temperature storage stability can be particularly poor with cellulose ethers in certain built, mixed anionic-nonionic liquid detergents. In cold weather, phase separation occurs and cellulose ether drops from suspension as gelatinous, ungainly lumps.
Accordingly, it is the prime object of this invention to provide a heavy duty liquid detergent containing cellulose ether that remains in homogeneous suspension even under freeze-thaw and low temperature storage conditions.